General ink-jet printers have served only as printers equipped with printheads to print images.
In contrast to this, a printer also having a scanner function by detachably mounting an image reading apparatus (scanner unit) on the carriage unit of the printer is known (see, for example, Japanese Patent Publication Nos. 1-20832, 2-21712, and 2-21711).
An image reading apparatus for outputting image data in one output form such as a serial output or 8-bit parallel output form has been used.
When the read data amount varies for each resolution, however, since the conventional image reading apparatus having only one output form has a low degree of flexibility in processing speed, power consumption associated with the processing speed, noise removing effect, and the like, high-precision image read cannot be performed.
More specifically, the image data read by the sensor in a required storage time must be transmitted as digital data. However, since an optimal combination of power consumption, processing speed, noise prevention, and the like cannot be selected, complicated control processing is required, resulting in low processing speed.
In addition, it is difficult to process noise based on digital signal processing and superimposed on an analog signal as a sensor output, i.e., noise (fixed noise) based on digital signal processing in a so-called analog/digital signal hybrid circuit. For this reason, high-precision image read cannot be performed.